Means for imparting twist to yarns



Nov. 3,1970 A. w. P. MACKINTOSH I MEANS FOR IIPARTING ms'r 'ro YARN-S 1 Filed April 25, 1969 United States Patent 3,537,250 MEANS FOR IMPARTING'TWIST T0 YARNS Alexander W. P. Mackintosh, 64 Main St., Evington, Leicester, England Filed Apr. 25, 1969, Ser. No. 819,160 Claims priority, application Great Britain, July 5, 1968, 32,188/ 68 Int. Cl. D01h 7/92 US. Cl. 57-774 '11 Claims ABSTRACT OF THE DISCLOSURE A twist head for imparting twist to yarns, has a central opening and trumpet-shaped ends each presenting an outwardly flared convex surface extending around an arc of 90. A yarn travelling diagonally through the head in a direction transverse to its axis has its respectively opposite sides frictionally contacted by surface portions moving in opposite directions. Each convex surface is grooved to receive a ring presenting a narrow friction-engendering surface area, the remainder of the convex surface being smooth. The trumpet-shaped ends may be extensions of the rotor of an electric motor, preferably of the four-pole shaped pole type. A yarn being twisted passes through the rotor and the motor speed determines the degree of twist.

This invention relates to means for imparting twist to yarns, and has for its object to provide an improvement in a twist head of a previously proposed form comprising a rotary annular component having a relatively small central opening which extends axially and merges into and connects ends (constituting the opposite sides of the twist head), these ends being trumpet-shaped and each presenting an outwardly flared convex surface of annular form extending around an arc of substantially 90, the said surfaces and the intermediate central opening connecting them being so related that a yarn or thread caused to travel diagonally through the component in a direction transverse to its axis of rotation not only has its respectively opposite sides frictionally contacted by surface portions moving in respectively opposite directions, but is supported for the major part of the distance both between the outer perimeter of the trumpet-shaped flare at one side of the head and the geometrical centre of the latter and also between the said centre and the outer perimeter of the similar flare of the opposite side of the head, whereby the yarn is fully controlled within the twist head and the twist generated in the yarn is prevented from springing through the twist head and so being nullified.

Although the present improvement is not necessarily limited in this respect, it is principally the intention to embody it in a twist head for imparting false twist to continuous multi-filament thermoplastic synthetic yarns such, for instance, as a polyamide or a polyester yarn.

It has been realised that the friction-engendering sur' faces of twist heads of the previously proposed form may, with advantage, vary in character, depending on the particular positions occupied by the heads in a yarn twisting machine or apparatus and thus, in appropriate cases, according to the stages of development of the twist in the progress of yarns through heaters generally provided in such a machine or apparatus for setting yarns whilst travelling in the twisted condition.

Thus, according to the present invention, the outwardly flared annular convex surface of each trumpet-shaped end of a twist head instead of being wholly or mainly of a uniform friction-engendering surface as heretofore, is adapted to present therearound only a comparatively narrow, and thus localised, effective friction-engendering surface area, the remainder of the convex surface being 'ice so smooth that the friction engendered thereby is practically negligible. In other words, the said remainder of the convex surface is, for all practical intents and purposes a substantially nonfriction surface.

Preferably, the said localised effective friction-engendering surface area at each end of the twist head is in the form of a narrow band or ring.

The quick starting and stopping of the twist heads may be facilitated by driving them independently, The trumpetshaped ends of annular components constituting the twist heads may, in accordance with a further feature of the invention, form extensions of the rotors of separate electric motors. As far as is known this is the first time that a textile yarn has been passed through the rotor of an electric motor for the purpose of having twist imparted thereto to a degree determined by the speed of the rotor.

In order that the invention may be more clearly understood and readily carried into practical effect, specific examples thereof will now be described with reference to the accompanying drawings, wherein:

FIG. 1 is a cross-sectional view, partly in elevation, of a pulley-driven form of the improved twist head,

FIG. .2 is a crosssectional view of a form of the improved twist head which itself incorporates an electric motor by which it is independently driven, and

FIG. 3 is a partly-exploded general perspective view of the twist head illustrated in FIG. 2.

Referring to the example illustrated in FIG. 1, it will be seen that the rotary annular component constituting the twist head TH comprises two coaxially and oppositely disposed elements 10 which, although initially separate, are rigidly connected together by an embracing bush 11, e.g., of Phosphor bronze. Small screws 12 are employed to secure the bush to the elements 10. The central portion of the twist head TH thus assembled extends axially and merges into and connects the trumpet-shaped ends 10a forming the opposite sides of the head. A relatively small central opening 13 in the said central portion merges into and connects outwardly flared convex surfaces 10b of annular form presented by the interiors of the trumpet-shaped ends 10a. The surface of each end of axially extending central opening 13 and the outwardly flared convex surface of the adjoining trumpet-shaped end 10a extend around an arc of substantially The middle portion of the central opening 13 is enlarged at 13a by virtue of recessing the inner end of each of the two abutted elements 10.

The bush 11 has combined therewith the inner rotary race 14a of a ball bearing 14 the stationary outer race 14b of which is in turn mounted within a housing 15. In an appropriate extended part 15a of this housing 15 is formed a tapped hole into which is screwed the inner end of a correspondingly screw-threaded stud 16 by means of which the twist head TH can be secured in its position of use in a yarn or thread twisting machine or apparatus.

In the example now being described each of the two trumpet-shaped ends 10a of the twist head is circumferentially grooved at to receive an endless V-belt (not shown) by means of which the head is driven from a separate power source.

In accordance with the characteristic feature of the present invention, the outwardly flared annular convex surfaoe 10b of each of the trumpet-shaped ends 10a of the twist head TH instead of being wholly or mainly of a uniform friction-engendering surface as heretofore, is adapted to present only a comparatively narrow and thus localised friction-engendering surface area.

Although, as previously mentioned, this localised friction-engendering area in each end 10a may be in the form of a narrow band of an extremely hard wearing material, the said area in the specific example illustrated is presented by the outermost portion 17a of the inner surface of a ring 17 which is set in an annular recess or groove within the trumpet-shaped end.

To ensure that it is fully effective upon a yarn or thread either entering or leaving the twist head TH, as the case may be, such a narrow band or the ring 17 may, if desired and as shown, be protuberant, i.e., raised slightly from the general curve of the outwardly flared convex surface b.

Advantageously, each narrow friction engendering band or the ring 17 may, as shown, be located approximately half way between the outer perimeter of the relevant trumpet-shaped flare 10b and the geometrical centre C of the twist head TH.

It is most important that the hereinbefore defined basic twist head shape shall be retained as this ensures maximum contact of yarns or threads with the narrow friction bands or rings.

The friction-engendering bands or rings must essentially be of an extremely hard wearing material. It is at present believed that a ceramic or a suitably hard or hardened abrasion-resistant metal will be required to withstand wear from yarns or threads continuously running over the bands or rings.

' The effect of the hereinbefore described improved twist head construction is to cause a yarn or thread to roll in a more precise manner. This can be compared with a gear action inasmuch that the number of turns imparted to a yarn or thread can be more nearly related to the ratio between the circumference of the yarn or thread and the appopriate circumference of the friction band or ring. Thus, the narrower it is practicable to make the friction band, or the smaller it is practicable to make the cross-section of the friction ring 17, as the case may be, the more nearly is it possible to achieve an exact gear ratio. 1

Referring again to FIG. 1, it will be noted that a yarn or thread, such as that designated Y, travelling in the direction of the arrows diagonally through the twist head TH and thus transversely to its axis a of rotation not only has its respectively opposite sides frictionally contacted by localised friction-engendering surface portions 17a moving in respectively opposite directions, but is also so supported by spaced portions of the outwardly flared convex surfaces 10b as to ensure its maximum contact with the friction rings 17.

In a yarn twisting process involving the use of a twist head TH, two travelling yards or threads Y and Y can be passed in opposite directions'through the head, the said yarns or threads being simultaneously twisted respectively opposite hand by virtue of having intersecting diagonally opposed portions maintained in contact with the relevant friction rings 17 at opposite sides of the head. The enlargement 13a of the central opening 13 provides the room necessary to ensure that the intersecting diagonally opposed portions of the said two yarns or threads, by virtue of being unsupported at this location, shall pass freely and without any obstruction from one flared end of the twist head to the other.

It is to be clearly understood that with the exception of the annular friction-engendering surface 17a presented by the ring 17, the remainder of the outwardly flared annular convex surface 10b of each of the trumpetshaped ends 10a is so smooth as to engender practically no friction.

. As regards the actual form of its trumpet-shaped ends 10a, the twist head TH illustrated in FIGS. 2 and 3 is similar to the twist head TH shown in FIG. 1. But in the twist head TI-I the two coaxial ends 10a are rigidly connected together by an embracing bush 18 having combined therewith the inner rotary races 19a of ball bearings 19. The outer stationary races 19b of these bearings are mounted within two spaced housing plates or blocks such as that clearly shown at 20 in FIG. 3.

The important differentiating feature of the twist head TH as compared with the twist head TH, however, is that it is driven by an electric motor constituting an actual. part of the head Although any appropriate form of elec tric motor may be employed for this purpose, a four-pole shaded pole motor is found to be eminently satisfactory. Thus, as will be seen in FIGS. 2 and 3, the rotor 21 of such a motor is interposed between the rotary ball bearing races 19:: and is secured to the bush 18. The laminated stator of the motor, indicated at 22, is firmly clamped in position between pairs of lateral lugs 20a and 20b of the two housing plates or blocks 20. The heads of bolts passed right through these pairs of lugs and interposed portions of the stator are designated 23. The rotor rotates within the stator 22 and there are associated with the latter two magnetic field-inducing coils 24 and 25 disposed at respectively opposite sides of the said rotor. The motor may conveniently be wholly encased within a casing 26 through which the outer portions of the trumpet-shaped ends 10a protrude.

The reason why a shaded pole type of motor is so satisfactory is that the stator is only about half an inch in width, this enabling a twist head to be kept desirably narrow and commensurately small in diameter.

The speed of a comparatively large number of motorised twist heads such as that just described incorporated into a yarn or thread twisting apparatus may be controlled by a frequency converter designed to change the cycles of the supply.

Although the herein described twist heads TH and TH are mounted to run on ball bearings, it is to be clearly understood that any other appropriate antifriction bearings capable of withstanding a high speed of the order of 6000 r.p.m. may be employed. For example, plain bearings, providing they are of a suitable material to withstand such a high speed, will suffice. Alternatively, a bearing in a magnetic field may be found to be satisfactory. Again, it would be possible to use a self-generating air bearing or even a bearing of the self-lubricating type.

Suitably disposed twist heads constructed in accordance with this invention enable progression twisting of yarns to take place in different angular directions. That is to say, such heads enable yarns to be satisfactorily twisted even when travelling through angular paths instead of along substantially straight paths as heretofore. These angular paths in turn enable the height of a yarn twisting machine or apparatus to be reduced to a minimum, and facilitate association with the twist heads of heaters for heating and thus setting the yarns whilst travelling in the twisted condition all as described in my copending US. patent application Ser. No. 611,920, filed J an. 26, 1967, now US. Pat. No. 3,451,206.

Such twist heads may advantageously also be incorporated into a complete yarn processing unit intimately associated with a knitting or other textile machine from which unit processed (false twisted) yarn is drawn upon by relevant instruments or elements of the machine intermittently and at varying speeds.

As will be appreciated, with twist heads of the improved construction incorporated into a processing unit as mentioned in the last preceding paragraph, there will be occasions when it is necessary to stop the twist heads rotating practically instantaneously with stoppage of the knitting or other textile machine. In accordance with a further feature of the invention, therefore, the twist heads may have combined therewith braking means of any appropriate character. Although such means may include electrically or/and electronically operated mechanical brakes adapted to hear, when applied, upon any convenient rotating parts of the twist heads, it is preferred to incorporate the electric motors of the twist heads in electric or/and electronic circuitry having means for effecting such a change in the characteristics of the current applied to the motors as to apply braking forces to the rotors thereof. For example, these means may function to convert A.C. current normally applied to the motors into a counter DC. current of substantially reduced voltage. Thus, with an A.C. current nominally of, say, 250 volts which is rectified and transformed to a counter D.C. current of only 50 volts, it is possible to stop a twist head rotating in a matter of one second.

I claim:

1. A twist head for imparting twist to yarns, said head comprising a rotary annular component having a central opening which extends axially and merges into and connects trumpet-shaped ends each presenting an outwardly flared convex surface of annular form extending around an arc of substantially 90, the said surfaces and the intermediate central opening being so related that a yarn caused to travel diagonally through the component in a direction transverse to its axis of rotation not only has its respectively opposite sides frictionally contacted by surface portions moving in respectively opposite directions, but is supported for a substantial part of the distance both between the outer perimeter of the trumpet-shaped flare a one side of the head and the geometrical centre of the latter, and also between the said centre and the outer perimeter of the similar flare at the opposite side of the head, whereby the yarn is controlled within the twist head and the twist generated in the yarn is prevented from springing through the twist head and so being nullified, said head being characterised in that the outwardly fiared annular convex surface of each trumpet-shaped end is adapted to present therearound only a comparatively narrow and thus localised eflective friction-engendering surface area, the remainder of the convex surface being so smooth that the friction engendered thereby is practically negligible.

2. A twist head according to claim 1, wherein the said narrow and localised effective friction-engendering surface area at each end of the head is presented by an initially separate ring which is set in an annular groove formed in the outwardly fiared convex surface of the relevant trumpet-shaped end.

3. A twist head according to claim 2, wherein each narrow and localised effective friction-engendering surface area is protuberant in that it is raised slightly from the general curse of the relevant outwardly flared convex surface to ensure that the friction ring is fully effective upon a yarn entering or leaving the twist head.

4. A twist nead according to claim 1, wherein each narrow and localised effective friction-engendering surface area is located approximately half way between the outer perimeter of the corresponding trumpet-shaped flare and the geometric centre of the twist head.

5. A twist head according to claim 1, wherein each of the trumpet-shaped ends is circumferentially grooved to receive a driving belt.

6. A twist head according to claim 1, wherein the trumpet-shaped ends constitute extensions of the rotor of an electric motor incorporated into the head whereby a yarn to be twisted passes through the said rotor and the degree of twist imparted is determined by the motor speed.

7. A motorised twist head according to claim 6, combined with means for braking the rotor of the electric motor.

8. A twist head according to claim 6, wherein the rotor is rotatable within a laminated stator having associated therewith coils for inducing a magnetic field.

9. A motorised twist head according to claim 8, which incorporates a four-pole shaded pole motor.

10. A motorised twist head according to claim 8, wherein the electric motor is incorporated in electric or/and electronic circuitry including means adapted to function, at desired times, to convert A.C. current normally applied to the stator coils into a counter DC. current of reduced voltage for the purpose of applying a braking force to the rotor.

11. A twist head for imparting twist to yarns, said head comprising a rotary annular component having a central opening which extends axially and merges into and connects trumpet-shaped ends each presenting an outwardly flared convex surface of annular form extending around an arc of substantially the said surfaces and the intermediate central opening being so related that a yarn caused to travel diagonally through the component in a direction transverse to its axis of rotation not only has its respectively opposite sides frictionally contacted by surface portions moving in respectively opposite directions, but is supported for a substantial part of the distance both between the outer perimeter of the trumpet-shaped flare at one side of the head and the geometrical centre of the latter, and also between the said centre and the outer perimeter of the similar flare at the opposite side of the head, whereby the yarn is controlled within the twist head and the twist generated in the yarn is prevented from springing through the twist head and so being nullified, said head being characterised in that the trumpet-shaped ends constitute extensions of the rotor of an electric motor incorporated into the head, said motor including a stator in which the rotor revolves and having combined therewith magnetic fleld-inducing coils, whereby a yarn to be twisted passes through the said rotor and the degree of twist imparted is determined by the motor speed.

References Cited FOREIGN PATENTS 1,180,583 12/1958 France. 1,252,321 6/ 1967 Germany.

378,458 6/ 1964 Switzerland.

JOHN PETRAKES, Primary Examiner 

